// Copyright © 2024 OpenIM. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package localcache

import (
	"context"
	"fmt"
	"math/rand"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/openimsdk/open-im-server/v3/pkg/localcache/lru"
)

func TestName(t *testing.T) {
	c := New[string](WithExpirationEvict())
	//c := New[string]()
	ctx := context.Background()

	const (
		num  = 10000
		tNum = 10000
		kNum = 100000
		pNum = 100
	)

	getKey := func(v uint64) string {
		return fmt.Sprintf("key_%d", v%kNum)
	}

	start := time.Now()
	t.Log("start", start)

	var (
		get atomic.Int64
		del atomic.Int64
	)

	incrGet := func() {
		if v := get.Add(1); v%pNum == 0 {
			//t.Log("#get count", v/pNum)
		}
	}
	incrDel := func() {
		if v := del.Add(1); v%pNum == 0 {
			//t.Log("@del count", v/pNum)
		}
	}

	var wg sync.WaitGroup

	for i := 0; i < tNum; i++ {
		wg.Add(2)
		go func() {
			defer wg.Done()
			for i := 0; i < num; i++ {
				c.Get(ctx, getKey(rand.Uint64()), func(ctx context.Context) (string, error) {
					return fmt.Sprintf("index_%d", i), nil
				})
				incrGet()
			}
		}()

		go func() {
			defer wg.Done()
			time.Sleep(time.Second / 10)
			for i := 0; i < num; i++ {
				c.Del(ctx, getKey(rand.Uint64()))
				incrDel()
			}
		}()
	}

	wg.Wait()
	end := time.Now()
	t.Log("end", end)
	t.Log("time", end.Sub(start))
	t.Log("get", get.Load())
	t.Log("del", del.Load())
	// 137.35s
}

// Test deadlock scenario when eviction callback deletes a linked key that hashes to the same slot.
func TestCacheEvictDeadlock(t *testing.T) {
	ctx := context.Background()
	c := New[string](WithLocalSlotNum(1), WithLocalSlotSize(1), WithLazy())

	if _, err := c.GetLink(ctx, "k1", func(ctx context.Context) (string, error) {
		return "v1", nil
	}, "k2"); err != nil {
		t.Fatalf("seed cache failed: %v", err)
	}

	done := make(chan struct{})
	go func() {
		defer close(done)
		_, _ = c.GetLink(ctx, "k2", func(ctx context.Context) (string, error) {
			return "v2", nil
		}, "k1")
	}()

	select {
	case <-done:
		// expected to finish quickly; current implementation deadlocks here.
	case <-time.After(time.Second):
		t.Fatal("GetLink deadlocked during eviction of linked key")
	}
}

func TestExpirationLRUGetBatch(t *testing.T) {
	l := lru.NewExpirationLRU[string, string](2, time.Minute, time.Second*5, EmptyTarget{}, nil)

	keys := []string{"a", "b"}
	values, err := l.GetBatch(keys, func(keys []string) (map[string]string, error) {
		res := make(map[string]string)
		for _, k := range keys {
			res[k] = k + "_v"
		}
		return res, nil
	})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if len(values) != len(keys) {
		t.Fatalf("expected %d values, got %d", len(keys), len(values))
	}
	for _, k := range keys {
		if v, ok := values[k]; !ok || v != k+"_v" {
			t.Fatalf("unexpected value for %s: %q, ok=%v", k, v, ok)
		}
	}

	// second batch should hit cache
	values, err = l.GetBatch(keys, func(keys []string) (map[string]string, error) {
		t.Fatalf("should not fetch on cache hit")
		return nil, nil
	})
	if err != nil {
		t.Fatalf("unexpected error on cache hit: %v", err)
	}
	for _, k := range keys {
		if v, ok := values[k]; !ok || v != k+"_v" {
			t.Fatalf("unexpected cached value for %s: %q, ok=%v", k, v, ok)
		}
	}
}